Venipuncture is the process of obtaining a sample of venous blood for purposes of performing various tests. Most samples are commonly obtained from a vein or organ that lies close to the surface of the skin. For example, usually the median cubital vein on the anterior forearm for venipunture.
Currently, venipunctures are executed manually by trained personnel, but there are problems inherent with these processes. Many times locating a vein is a challenge, especially in younger and elderly individuals. To complicate matters, multiple attempts at needle insertion may be required, due either to the inexperience of the person obtaining the sample, and/or from difficulty in locating the target vein, resulting in discomfort to the patient and bruising.
It was first demonstrated in the 1930s that infrared light can be used to image subcutaneous veins, based on the principle that near infrared (NIR) light has the ability to penetrate human tissue better than visible light and is differentially absorbed by oxygenated and deoxygenated hemoglobin. Skin and some other body tissues reflect infrared light in the near-infrared wavelength range of about 700 to 900 nanometers, while blood absorbs radiation in this range. Thus, in video images of body tissue taken under infrared illumination, vessels, e.g. blood vessel or organs, appear as dark lines against a lighter background of surrounding fatty tissue. Therefore, a target vessel can be “illuminated” by finding the positions where the light absorption difference between deoxyhemoglobin and oxyhemoglobin is the greatest.
To aid in locating target veins for venipunture, some companies have commercialized systems using imaging techniques—one example is Lumintex's VeinViewer. This device detects subcutaneous veins and projects a real time image back on the skin, providing a two-dimensional (2D) positional guide for venipuncture. Although this technology may provide methods of viewing veins externally, it does not provide any depth representation of the veins under the skin, leaving the question of how far and deep to insert the needle to a human estimation. The actual venipuncture must therefore be performed manually, leading to the inevitable human error.
Some ongoing studies have resulted in a pseudo three-dimensional (3D) imaging systems to serve as the guidance for an automatic catheterization device. These methods use near infrared (NIR) imaging to localize and map superficial veins and a separate NIR based laser system to generate a 3D topological map of the skin surface. Two-dimensional (2D) masks of the vessels are generated and then projected onto the 3D topological maps. In this system, only an estimation of actual vessel position is generated, because no measurements of vessel depth from the surface of the skin are ever computed. Therefore, when attempting to guide the needle into the vein, there is no accurate value as to how deep to drive the needle.
There is also broad research being performed that will robotically guide a needle. One company, ImageGuide, Inc. (part of GE Medical Systems), uses this technology in conjunction with current commercial imaging systems such as CT and MR. These methods, however, use cumbersome and non-portable devices for both the viewing and robotics. Currently, there is no commercial technology that combines an imaging system with a robotically driven needle in a portable unit for the purpose of venipuncture.